"And if a vacuum be formed?"
"Then the sound is totally extinguished."
"So, then," objected Willis, "if two persons were to talk in what you call a vacuum, they would not hear each other?"
"Two persons could not talk in a vacuum," replied Ernest.
"Why not?"
"Because they would die as soon as they opened their mouths."
"Ah, that alters the case."
"If, on the contrary, a quantity of air or gas were compressed into a space beyond what it habitually held, then the sound," continued Ernest, "would be more intense than if the air were free."
"In that case a whisper would be equal to a howl!"
"You think I am joking, Willis; but on the tops of high mountains, such as the Himalaya and Mont Blanc, where the air is much rarified, voices are not heard at the distance of two paces."